Physiology - The Nucleus

Introduction

• Continuation of the playlist on physiology.
• Previous video: Cell Membrane.
• Current topic: The Nucleus, the control center of the cell.

Recap of Cell Organelles

• Mitochondria: Powerhouse
• Lysosome: Soldier
• Endosome: Delivery guy
• Endoplasmic Reticulum:
  • Rough: Translator
  • Smooth: Like a doughnut
• Golgi Apparatus: Sorter
• Peroxisomes: Gym trainer

Historical Background

• Discovered by Antony van Leeuwenhoek, who called it 'nut', 'carrion', or 'nucleus'.
• Greek term for nucleus: 'carrion'.
• Term 'Carrio lysis':
  • Carrio = Nucleus
  • Lysis = Destruction/Dissolution

Structure and Function of the Nucleus

• Largest organelle in animal cells
• Control Center: Contains genetic material (DNA).
• DNA and Chromosomes:
  • DNA packed into chromosomes.
  • Enclosed by nuclear membrane with pores.
• Maintains Integrity of Genes
  • Genes are parts of DNA.
• Nucleoplasm:
  • Also known as karyolymph.
  • Viscous liquid inside nucleus.

Nuclear Membrane

• Envelope Surrounding Nucleus
• Double Membrane:
  • Outer and inner membrane.
  • Intermembrane space: Peri-nuclear space.
• Maintains Internal Environment
  • Separates nucleus from cytoplasm.
• Membrane Pores:
  • Selective exchange of molecules and ions.
  • Outer membrane continuous with rough endoplasmic reticulum.
• Studded with Ribosomes

DNA Structure

• Encyclopedia of the Cell
• Double Helix when unpacked
• Chromatin and Chromosomes when packed
  • 46 chromosomes in somatic cells.

DNA Transcription and Protein Synthesis

• DNA to RNA (mRNA)
• mRNA exits nucleus through pores
  • Translated into proteins in cytoplasm.

The Nucleolus

• Means 'Small Nucleus'
  • Occupies a quarter of the nucleus.
  • No membrane.
• Function:
  • Assembly of ribosomes.
  • Synthesis of RNA.
• Enlarges when synthesizing proteins

Nuclear Matrix

• Support Structure of Nucleus
• Includes Nuclear Lamina
  • Subtype of intermediate filaments.

Variations in Nucleus

• Most cells have one nucleus.
• Exceptions:
  • Red blood cells have none.
  • Osteoclasts have multiple nuclei.
  • White blood cells: Segmented nucleus (bi-lobed, tri-lobed).

Function of Pores

• Passage of large molecules.
• Small molecules or ions can diffuse.

Conclusion

• Next video: Focus on the nucleolus.
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